This invention relates to a system for dispensing to and withdrawing a fluid medium from a balloon catheter for dilatation purposes.
This invention also relates to a stent expansion system comprising a balloon catheter with a tubular shaft having proximal and distal portions, a dilatation balloon mounted on the distal portion of the shaft for expanding an expandable stent, a fluid supply lumen extending throughout the shaft for balloon inflation, and a pressure source for dispensing to and withdrawing a fluid medium from the balloon via the supply lumen.
The invention further relates to a machine for pulsating the medium inflating the balloon of a catheter arrangement having a shaft, a dilatation balloon mounted on the shaft, a fluid supply lumen extending throughout the shaft for balloon inflation, and a pressure source for dispensing to and withdrawing a fluid medium from the balloon via the lumen.
The invention still further relates to a balloon catheter with a tubular shaft having proximal and distal portions, a dilatation balloon mounted on the distal portion of the shaft, and a fluid supply lumen extending throughout the shaft for balloon inflation.
Balloon catheters are quite currently used for dilating vessels or other body cavities. To this end, the balloon is positioned at the area to be dilated and then fed with a fluid medium to achieve dilatation and thereby expand the vessel. During the treatment, the vessel is occluded by the balloon and the blood supply to the upstream organs is interrupted. A further problem is that some occlusions cannot be dilated because the vessel has achieved a rigidity resisting the dilating pressure executed by the balloon.
U.S. Pat. No. 4,439,186 describes a dilatation catheter with an expandable balloon in communication with an inflation lumen extending along the length of the catheter. The balloon has a pressure-volume relationship which is not linear, and a pressure source is provided which supplies a pulsating pressure to the balloon for alternating expansion and contraction thereof. The source of fluctuating pressure comprises a pump supplying a fluid to a container filled with the fluid and which is provided with a flexible bottom connected to the magnetic core of an electromagnet. The container is connected to the dilatation balloon and energizing of the electromagnet causes the magnetic core to move the flexible bottom of the container, thus producing a corresponding pressure pulse or a series of pressure pulses in the fluid within the container. By alternating expansion and contraction of the balloon the blood may circulate during the periods of time during which the vessel is not under is action of the balloon. Connection of the container of pressure fluid to the core of an electromagnet requires serious insulation measures in order to avoid any risk of having the patient or other attendant materials in contact with electric current.
U.S. Pat. No. 5,152,776 shows a dilatation balloon catheter fed by a pump controlled by a drive mechanism. The actual fluid conditions present in the balloon are identified by a monitor and communicated to a microprocessor sending orders to the drive mechanism in accordance with a predetermined pattern in order to prevent prolonged cessation of blood flow to sites distal from the action. This structure does not allow the feed of any pulsating pressure to the balloon.
U.S. Pat. No. 4,446,867 shows a fluid driven balloon catheter comprising a catheter with a through going lumen, a fluid supply inflation device attached to one end of the catheter, and a balloon attached to the other end. A pulse generator is provided for generating pressure pulses in the fluid through the lumen to sharply expand and contract the balloon at intervals. This pulse generator comprises a pulse inflation device communicating with the catheter lumen via a T joint and valve, a spring driven ram to bump upon the piston of the pulse inflation device, and a cam rotor to move the ram away from the piston of the pulse inflation device, whereby when the cam moves the ram away from the piston of the pulse inflation device, the spring of the ram is compressed until the cam rotates further and releases the ram to strike the piston of the pulse inflation device. By this pulse action, it is said that the occlusive material in the vessel, which is more brittle than the surrounding vessel wall will crack. However, the friction of the piston in the pulse inflation device of the pulse generator will substantially damp down the pulse action. Furthermore, the hammer operation of the spring loaded ram may cause non negligible stresses on both the piston and pulse inflation device.
The balloon catheter is also an instrument of common use as a mechanism for transporting and applying by expansion a balloon expandable prosthesis, called a stent, for maintaining the patency of a vessel. It is also used for completing the expansion of self-expandable stents which are not transported and applied by a balloon catheter but by a specially devised hollow catheter.
Expansion of a stent requires however a relatively high pressure in the balloon, at least for the last stage force needed to seat or press the stent against the vessel wall. High balloon pressures may induce the risk of overpressure causing trauma to the vessel wall; they also induce the risk of bursting the balloon and further wounding the patient. Furthermore, it is difficult to modulate the pressure in the balloon to precisely control the stent expansion and its embedding into the vessel wall. These difficult conditions need a lot of attention for the expansion manipulation, which is an added load for the practitioner.
There is no suggestion in the documents referred to hereinabove that pulsation of the fluid medium feeding a balloon catheter could be envisaged as a help for stent expansion. Moreover, it has always been considered that a sharp highblow is the way to properly expand and seat a stent in the vessel wall.
It is an object of this invention to propose a fluid delivery for a balloon catheter and a stent expansion system which are highly versatile, simple to manufacture, and easy to use. A further object of the invention is to propose a machine for pulsating the fluid medium inflating the balloon of a balloon catheter arrangement which is highly versatile and very easy to operate, which is simple to manufacture, and which affords a high degree of safety for the patient. Still a further object of the invention is a balloon catheter particularly adapted for a versatile usage.
In sum, the present invention relates to a system for dispensing and withdrawing a fluid medium to and from a balloon catheter for balloon dilatation purposes, and especially the improvement of means for pulsating the fluid medium when dispensed to the balloon for stepwise expansion of an expandable stent. The stent expansion system may have a balloon catheter with a tubular shaft having proximal and distal portions, a dilatation balloon mounted on the distal portion of the shaft for expanding an expandable stent, a fluid supply lumen extending throughout the shaft for balloon inflation, a pressure source for dispensing and withdrawing a fluid medium to and from the balloon via the supply lumen, and means for pulsating the fluid medium when dispensed to the balloon. The means for pulsating the fluid medium may squeeze the tubular shaft and may sequentially squeeze and release the tubular shaft. The tubular shaft may have in the vicinity of its proximal portion a first region having a first softness and a second region distal of the first region having a second softness, wherein the first softness is greater than the second softness, and wherein the means for pulsating the fluid medium squeeze the tubular shaft in the first region. The tubular shaft may have a third region proximal of the first region, the third region having a softness smaller than that of the first region. The second and third regions may have the same softness. The first region of the tubular shaft may be detachable.
The present invention also relates to a machine for pulsating the fluid medium inflating a balloon of a balloon catheter arrangement. The machine may have a shaft, a dilatation balloon mounted on the shaft, a fluid supply lumen extending throughout the shaft for balloon inflation, a pressure source for dispensing and withdrawing a fluid medium to and from the balloon via the lumen, and saddle means for bearing a portion of the shaft and ram means for squeezing the portion of the shaft against the saddle means. The machine may also have means for reciprocating the cam means towards and away from the saddle means, and the reciprocating means may be motor driven cam means. The machine may also have groove means for positioning the shaft with respect to the ram and saddle means. The machine may also have box means for containing one of the saddle means and ram means, cover means for containing the other of the saddle means and ram means, and means for positioning the cover means on the box means. The machine may also have means for locking the cover means on the box means.
The present invention also relates to a balloon catheter with a tubular shaft having proximal and distal portions, a dilatation balloon mounted on the distal portion of the shaft, and a fluid supply lumen extending throughout the shaft for balloon inflation, wherein the tubular shaft has in the vicinity of its proximal portion a first region having a first softness and a second region distal of the first region and having a second softness, wherein the first softness is greater than the second softness. The first region of the tubular shaft may be detachable. The tubular shaft may be a third region proximal of the first region, the third region having a softness smaller than that of the first region.
The present invention also relates to a medical device having a catheter with a tubular shaft defining a lumen, the catheter having a proximal portion and a distal portion; a balloon mounted on the catheter distal portion and in fluid communication with the lumen; and means for applying force to the catheter shaft at a predetermined location thereby constricting a diameter of the lumen at or about the predetermined location and causing an increase in pressure within the balloon. The means for applying force may be adapted to sequentially squeeze and release the catheter shaft at the predetermined location to cause the balloon to pulsate. The present invention also relates to a method of expanding a stent including delivering a stent to a treatment site, the stent having an interior surface; delivering a balloon catheter to the treatment site, the balloon catheter comprising a tubular shaft defining a lumen, the catheter having a proximal portion and a distal portion, a balloon mounted on the catheter distal portion and in fluid communication with the lumen, and means for applying force to the catheter shaft at a predetermined location thereby constricting a diameter of the lumen at or about the predetermined location and causing an increase in pressure within the balloon, wherein the balloon catheter is delivered such that the balloon is disposed within the stent; and applying force to the catheter shaft at the predetermined location thereby constricting the diameter of the lumen at or about the predetermined location and causing an increase in pressure within the balloon, in turn causing the balloon to apply force to the stent interior surface. The force may be applied by sequentially squeezing and releasing the catheter shaft at the predetermined location causing the balloon to pulsate.
Accordingly, by use of means for pulsating the fluid medium dispensed to the balloon for the stepwise expansion of an expandable stent, as well as by the stent expansion system comprising means for pulsating the fluid medium dispensed to the balloon, the expansion of the stent is achieved by a vibrating strength which causes a succession of very small increments in the radial size of the stent; a better, more uniform and less brutal embedding of the stent in the vessel wall is obtained; the trauma to the vessel wall is reduced and the fluid pressure may be substantially lower than usual.
Where the means for pulsating the fluid medium squeeze the tubular shaft, the pulsation is obtained by action external to the fluid medium, there is no damping of the pulse action, and there is no need for additional fluid containers to be acted upon by electrical equipment. And the means for pulsating the liquid medium may sequentially squeeze and release the tubular shaft without affecting or being affected by the undamped pulse action.
The tubular shaft may comprise in the vicinity of its proximal portion a first region having a first softness and a second region distal of the first region and having a second softness, with the first softness being greater than the second softness and the means for pulsating the fluid medium squeezing the tubular shaft in the first region. A squeeze region is thus created in the tubular shaft which has characteristics different from those of the other portions of the tubular shaft which may thus retain its original characteristics of flexibility, pushability and resistance to kinking.
Where the tubular shaft comprises a third region proximal of the first region and having a softness smaller than that of the first region, the system may be made on the basis of standard catheter elements in which only the first portion has the required softer condition. To further take advantage of standard catheter elements, the second and third regions may have the same softness. And when the first region of the tubular shaft is detachable, the system may be achieved on the basis of a standard catheter shaft with a squeeze portion which may be selected at will, in view of the pulsating conditions which are sought.
As the machine for pulsating the fluid medium comprises saddle means for bearing a portion of the catheter shaft and ram means for squeezing the portion of the tubular shaft against the saddle means, such a machine constitutes a fully independent pulsating equipment for the fluid medium feeding the balloon catheter. There are no stresses on equipment components and no added fluid containers to obtain the pulsation. The balloon catheter may be handled separately for sterilization purposes and the person manipulating the catheter may proceed with sterilized gloves, without handling the machine which may be operated by another person.
Where the machine comprises means for reciprocating the ram means towards and away from the saddle means, a very simple mechanization may be achieved, preferably by means of motor driven cam means. The latter allows easy and rapid change of the pulsation by mere variation of the motor speed or change of the cam means.
The machine may comprise groove means for positioning the shaft with respect to the ram and saddle means, whereby a very simple and fail proof locating of the shaft in the machine.
The machine may comprise box means containing one of the saddle means and ram means, cover means for containing the other of the saddle and ram means, and means for positioning the cover means on the box means, with the possibility of having means for locking the cover means on the box means. This results in a closed, self-contained, error proof unit which can be permanently placed in an appropriate location of the operating room or which can be brought in any convenient place in the operating room to be available upon need of pulsating the fluid medium in a balloon catheter.
As the tubular shaft of the balloon catheter comprises in the vicinity of its proximal portion a first region having a first softness and a second region distal of the first region and having a second softness, with the first softness being greater than the second softness, the balloon catheter is particularly adapted to having its first region squeezed for pulsating the fluid medium used to feed the balloon. And where this first region is detachable and/or preceded by a third region having a smaller softness, use can be made of a standard catheter with attachment of the region specifically adapted to squeeze pulsation.